Ultra-high modulus and etch selectivity boron-carbon hardmask films

ABSTRACT

Implementations of the present disclosure generally relate to the fabrication of integrated circuits. More particularly, the implementations described herein provide techniques for deposition of boron-carbon films on a substrate. In one implementation, a method of processing a substrate is provided. The method comprises flowing a hydrocarbon-containing gas mixture into a processing volume of a processing chamber having a substrate positioned therein, wherein the substrate is heated to a substrate temperature from about 400 degrees Celsius to about 700 degrees Celsius, flowing a boron-containing gas mixture into the processing volume and generating an RF plasma in the processing volume to deposit a boron-carbon film on the heated substrate, wherein the boron-carbon film has an elastic modulus of from about 200 to about 400 GPa and a stress from about −100 MPa to about 100 MPa.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/233,351, filed Aug. 10, 2016, which claims benefit of U.S.Provisional Patent Application No. 62/239,645, filed Oct. 9, 2015, allof which are herein incorporated by reference in their entireties.

BACKGROUND Field

Implementations of the present disclosure generally relate to thefabrication of integrated circuits. More particularly, theimplementations described herein provide techniques for deposition ofboron-carbon films on a substrate.

Description of the Related Art

Integrated circuits have evolved into complex devices that can includemillions of transistors, capacitors and resistors on a single chip. Theevolution of chip designs continually calls for faster circuitry andgreater circuit density. The demands for faster circuits with greatercircuit densities impose corresponding demands on the materials used tofabricate such integrated circuits. In particular, as the dimensions ofintegrated circuit components are reduced to the nanometer scale, it isnow necessary to use low resistivity conductive materials as well as lowdielectric constant insulating materials to obtain suitable electricalperformance from such components.

The demands for greater integrated circuit densities also impose demandson the process sequences used in the manufacture of integrated circuitcomponents. For example, in process sequences that use conventionalphotolithographic techniques, a layer of energy sensitive resist isformed over a stack of material layers disposed on a substrate. Theenergy sensitive resist layer is exposed to an image of a pattern toform a photoresist mask. Thereafter, the mask pattern is transferred toone or more of the material layers of the stack using an etch process.The chemical etchant used in the etch process is selected to have agreater etch selectivity for the material layers of the stack than forthe mask of energy sensitive resist. That is, the chemical etchantetches the one or more layers of the material stack at a rate muchfaster than the energy sensitive resist. The etch selectivity to the oneor more material layers of the stack over the resist prevents the energysensitive resist from being consumed prior to completion of the patterntransfer.

As the pattern dimensions are reduced, the thickness of the energysensitive resist must correspondingly be reduced in order to controlpattern resolution. Such thin resist layers can be insufficient to maskunderlying material layers during the pattern transfer step due toattack by the chemical etchant. An intermediate layer, called ahardmask, is often used between the energy sensitive resist layer andthe underlying material layers to facilitate pattern transfer because ofits greater resistance to the chemical etchant. It is desirable to havethin hardmasks that have both high etch selectivity and are easy toremove after the etching process is complete. As critical dimensions(CD) decrease, current hardmask materials lack the desired etchselectivity relative to underlying materials and are often difficult toremove.

Boron-carbon films have good mechanical properties, excellent stepcoverage, good wet etch resistance and a high dry etch selectivity forlow dielectric films. All of these characteristics are beneficial forapplications such as lithographic hard masks to low-k dielectric etchingand self-aligned double-patterning processes. However, due to theiramorphous nature, amorphous boron films tend to have a high film stresswhich causes line bending damaging the integrated circuit. Amorphouscarbon films have poor etch selectivity, which necessitates thickhardmasks. Thick hardmasks are not suitable due to decreasedtransparency, and pattern bending or collapse at higher aspect ratios.

Therefore there is a need for a transparent hardmask film with improvedetch selectivity. There is also a need for methods for depositingimproved hardmask layers.

SUMMARY

Implementations of the present disclosure generally relate to thefabrication of integrated circuits. More particularly, theimplementations described herein provide techniques for deposition ofboron-carbon films on a substrate. In one implementation, a method ofprocessing a substrate is provided. The method comprises flowing ahydrocarbon-containing gas mixture into a processing volume of aprocessing chamber having a substrate positioned therein, wherein thesubstrate is heated to a substrate temperature from about 400 degreesCelsius to about 700 degrees Celsius, flowing a boron-containing gasmixture into the processing volume and generating an RF plasma in theprocessing volume to deposit a boron-carbon film on the heatedsubstrate, wherein the boron-carbon film has an elastic modulus of fromabout 200 GPa to about 400 GPa and a stress from about −100 MPa to about100 MPa.

In another implementation, a method of processing a substrate isprovided. The method comprises flowing a hydrocarbon-containing gasmixture into a processing volume of a processing chamber having asubstrate positioned therein, wherein the substrate is heated to asubstrate temperature from about 400 degrees Celsius to about 700degrees Celsius, and wherein the boron-containing gas mixture comprisesdiborane (B₂H₆), flowing a boron-containing gas mixture into theprocessing volume, wherein the hydrocarbon-containing gas mixturecomprises propylene (C₃H₆), and generating an RF plasma in theprocessing volume to deposit a boron-carbon film on the heatedsubstrate, wherein the boron-carbon film has an elastic modulus of fromabout 200 to about 400 GPa and a stress from about −100 MPa to about 100MPa.

In yet another implementation, a method of processing a substrate isprovided. The method comprises flowing a hydrocarbon-containing gasmixture into a processing volume of a processing chamber having asubstrate positioned therein, wherein the substrate is heated to asubstrate temperature from about 400 degrees Celsius to about 700degrees Celsius, flowing a boron-containing gas mixture into theprocessing volume, stabilizing a pressure in the processing volume for apredefined RF-on delay time period, generating an RF plasma in theprocessing volume to deposit a boron-carbon film on the heatedsubstrate, wherein the boron-carbon film has an elastic modulus of fromabout 200 to about 400 GPa and a stress from about −100 MPa to about 100MPa, forming a patterned photoresist layer over the boron-carbon film,etching the boron-carbon film in a pattern corresponding with thepatterned photoresist layer, etching the pattern into the substrate, anddepositing a material into the etched portions of the boron-carbon film.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 depicts a schematic illustration of an apparatus that can be usedfor the practice of implementations described herein;

FIG. 2 depicts a process flow diagram depicting one implementation of amethod for depositing a boron-carbon film according to implementationsdescribed herein;

FIG. 3 depicts a schematic cross-sectional view of a substrate structureincorporating a boron-carbon film as a hardmask layer according toimplementations described herein;

FIG. 4A is a plot illustrating the effect of temperature and boronincorporation on the deposition rate of boron-carbon films according toimplementations described herein;

FIG. 4B is a plot illustrating the effect of temperature and boronincorporation on the optical properties of boron-carbon films accordingto implementations described herein;

FIG. 4C is a plot illustrating the effect of temperature and boronincorporation on the film density of boron-carbon films according toimplementations described herein;

FIG. 4D is a plot illustrating the effect of temperature and boronincorporation on the stress of boron-carbon films according toimplementations described herein;

FIG. 5A is a plot illustrating the effect of pressure on the stress andfilm density of boron-carbon films according to implementationsdescribed herein;

FIG. 5B is a plot illustrating the effect of spacing on the stress andfilm density of boron-carbon films according to implementationsdescribed herein;

FIG. 6 is a bar graph illustrating the effect of boron percent on oxideetch selectivity and tungsten etch selectivity for boron-carbon filmsaccording to implementations described herein;

FIG. 7A is a bar graph illustrating the effect of temperature on theoxide etch selectivity and stress of boron-carbon films according toimplementations described herein;

FIG. 7B is a bar graph illustrating the effect of nitrogen flow rate onthe oxide etch selectivity and stress of boron-carbon films according toimplementations described herein;

FIG. 7C is a bar graph illustrating the effect of temperature on thetungsten/silicon etch selectivity and stress of boron-carbon filmsaccording to implementations described herein; and

FIG. 7D is a bar graph illustrating the effect of nitrogen flow rate onthe tungsten/silicon etch selectivity and stress of boron-carbon filmsaccording to implementations described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation. It is to be noted, however, that theappended drawings illustrate only exemplary implementations of thisdisclosure and are therefore not to be considered limiting of its scope,for the disclosure may admit to other equally effective implementations.

DETAILED DESCRIPTION

The following disclosure describes techniques for deposition ofboron-carbon films on a substrate with high modulus and etchselectivity. Certain details are set forth in the following descriptionand in FIGS. 1-7D to provide a thorough understanding of variousimplementations of the disclosure. Other details describing well-knownstructures and systems often associated with boron-carbon films are notset forth in the following disclosure to avoid unnecessarily obscuringthe description of the various implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Hardmasks having high etch selectivity are the cornerstone fordevelopment of devices of ˜10 nanometers or smaller in dimension.Current low temperature boron-containing carbon hardmasks achieve goodetch selectivity, mechanical strength, transparency and ease ofstripping compared to previous amorphous carbon hardmask films. However,the amorphous nature, higher incorporated hydrogen and lower modulus(˜100 GPa) of low temperature boron-containing hardmask films limitfabrication of high aspect-ratio features and smaller dimension devices.To enable next-generation integrated circuit chipsets, implementationsof the present disclosure provide for the fabrication of high-densityboron-carbon hardmask films at higher temperatures (e.g., ≥400 degreesCelsius). Implementations of the high-density boron-carbon hardmaskfilms described herein have reduced in-film H₂ content and increasedmodulus compared to currently available low temperature boron-containinghardmask films, while maintaining lower stress, transparency and highdeposition rates. The ultra-high etch selectivity of boron-carbonhardmask films described herein allow single-pass pattern transfer ofhigh-aspect ratio features in future generations of NAND and DRAMdevices. The boron-carbon hardmask films described herein are wellsuited for 7-10 nanometer devices due to their resistance to patterncollapse, excellent critical dimension (“CD”) control and higher patternresolution. Additionally, due to extreme etch selectivity to underlyinglayers; the boron-carbon hardmask films described herein are thinner(e.g., about 30% to 40% thinner for the same device dimensions) incomparison to current films, which would reduce deposition and strippingtime. Implementations of the present disclosure, provide boron-carbonfilms having ultra-high modulus (≥200 GPa) and high etch selectivity(>4× improvement over current hardmask films).

Films can be deposited using various carbon precursors (e.g., propylene,acetylene, ethylene, methane, hexane, hexane, isoprene, butadiene etc.),boron sources (e.g., diborane (B₂H₆), orthocarborane andtrimethylborazine); and nitrogen containing precursors (e.g., pyridine,aliphatic amine, amines, nitriles, ammonia). Based on the systematicanalysis of different film deposition parameters including temperature(e.g., 400 to 700 degrees Celsius; 550 to 650 degrees Celsius), pressure(e.g., 2 to 20 Torr; 10 to 20 Torr), boron precursor flow rate (e.g.,100-6,000 sccm), H₂ dilution of the boron precursor (e.g., 2 to 20%),and RF power (e.g., 500 to 2,500 Watts) it was determined that at highertemperatures, the extinction coefficient (k) and stress aresignificantly higher than at low temperatures.

Higher k and stress adversely affect film composition, and aredetrimental to photolithographic pattern transfer. At very high filmstresses, residual stress caused the film to peel-off from theunderlying layer or causes high particle defects. Similarly, theabsorption/extinction coefficient of film strongly depends ontemperature, and is driven by morphology and molecular structureamorphous carbon structure (i.e. sp²/sp³ binding) and boronincorporation. Hence, implementations described herein provide filmdeposition parameters (B₂H₆ flow, substrate to electrode spacing, RFpower, chamber pressure, etc.) for depositing boron-carbon films thathaving <0.01 k and <+/−100 MPa stress.

Implementations described herein will be described below in reference toa PECVD process that can be carried out using any suitable thin filmdeposition system. Examples of suitable systems include the CENTURA®systems which may use a DxZ™ processing chamber, PRECISION 5000®systems, PRODUCER™ systems, PRODUCER GT™ and the PRODUCER SE™ processingchambers which are commercially available from Applied Materials, Inc.,of Santa Clara, Calif. Other tools capable of performing PECVD processesmay also be adapted to benefit from the implementations describedherein. In addition, any system enabling the PECVD processes describedherein can be used to advantage. The apparatus description describedherein is illustrative and should not be construed or interpreted aslimiting the scope of the implementations described herein.

The term “about” generally indicates within ±0.5% or up to 1% of theindicated value. In addition, the term “about” can indicate either ameasurement error (i.e., by limitations in the measurement method), oralternatively, a variation or average in a physical characteristic of agroup (e.g., a population of pores).

FIG. 1 depicts a schematic illustration of a substrate processing system132 that can be used to perform amorphous carbon layer deposition inaccordance with implementations described herein. The substrateprocessing system 132 includes a processing chamber 100 coupled to a gaspanel 130 and a controller 110. The processing chamber 100 generallyincludes a top 124, a side 101 and a bottom wall 122 that define aninterior processing volume 126. A support pedestal 150 for supporting asubstrate 190 is positioned in the interior processing volume 126 of theprocessing chamber 100. The support pedestal 150 is supported by a stem160 and may be typically fabricated from aluminum, ceramic, and othersuitable materials. The support pedestal 150 may be moved in a verticaldirection inside the processing chamber 100 using a displacementmechanism (not shown).

The support pedestal 150 may include an embedded heater element 170suitable for controlling the temperature of the substrate 190 supportedon a surface 192 of the support pedestal 150. The support pedestal 150may be resistively heated by applying an electric current from a powersupply 106 to the embedded heater element 170. The embedded heaterelement 170 may be made of a nickel-chromium wire encapsulated in anickel-iron-chromium alloy (e.g., INCOLOY®) sheath tube. The electriccurrent supplied from the power supply 106 is regulated by thecontroller 110 to control the heat generated by the embedded heaterelement 170, thus maintaining the substrate 190 and the support pedestal150 at a substantially constant temperature during film deposition. Thesupplied electric current may be adjusted to selectively control thetemperature of the support pedestal 150 between about 400 degreesCelsius to about 700 degrees Celsius.

A temperature sensor 172, such as a thermocouple, may be embedded in thesupport pedestal 150 to monitor the temperature of the support pedestal150 in a conventional manner. The measured temperature is used by thecontroller 110 to control the power supplied to the embedded heaterelement 170 to maintain the substrate 190 at a desired temperature.

A vacuum pump 102 is coupled to a port formed in the bottom of theprocessing chamber 100. The vacuum pump 102 is used to maintain adesired gas pressure in the processing chamber 100. The vacuum pump 102also evacuates post-processing gases and by-products of the process fromthe processing chamber 100.

The substrate processing system 132 may further include additionalequipment for controlling the chamber pressure, for example, valves(e.g. throttle valves and isolation valves) positioned between theprocessing chamber 100 and the vacuum pump 102 to control the chamberpressure.

A gas distribution assembly 120 having a plurality of apertures 128 isdisposed on the top of the processing chamber 100 above the supportpedestal 150. The apertures 128 of the gas distribution assembly 120 areutilized to introduce process gases into the processing chamber 100. Theapertures 128 may have different sizes, number, distributions, shape,design, and diameters to facilitate the flow of the various processgases for different process requirements. The gas distribution assembly120 is connected to the gas panel 130 that allows various gases tosupply to the interior processing volume 126 during process. Plasma isformed from the process gas mixture exiting the gas distributionassembly 120 to enhance thermal decomposition of the process gasesresulting in the deposition of material on a surface 191 of thesubstrate 190.

The gas distribution assembly 120 and support pedestal 150 may form apair of spaced apart electrodes in the interior processing volume 126.One or more RF power sources 140 provide a bias potential through amatching network 138 to the gas distribution assembly 120 to facilitategeneration of plasma between the gas distribution assembly 120 and thesupport pedestal 150. Alternatively, the RF power sources 140 andmatching network 138 may be coupled to the gas distribution assembly120, the support pedestal 150, or coupled to both the gas distributionassembly 120 and the support pedestal 150, or coupled to an antenna (notshown) disposed exterior to the processing chamber 100. In oneimplementation, the RF power sources 140 may provide between about 100Watts and about 3,000 Watts at a frequency of about 50 kHz to about 13.6MHz. In another implementation, the RF power sources 140 may providebetween about 500 Watts and about 1,800 Watts at a frequency of about 50kHz to about 13.6 MHz.

The controller 110 includes a central processing unit (CPU) 112, amemory 116, and a support circuit 114 utilized to control the processsequence and regulate the gas flows from the gas panel 130. The CPU 112may be of any form of a general-purpose computer processor that may beused in an industrial setting. The software routines can be stored inthe memory 116, such as random access memory, read only memory, floppy,or hard disk drive, or other form of digital storage. The supportcircuit 114 is conventionally coupled to the CPU 112 and may includecache, clock circuits, input/output systems, power supplies, and thelike. Bi-directional communications between the controller 110 and thevarious components of the substrate processing system 132 are handledthrough numerous signal cables collectively referred to as signal buses118, some of which are illustrated in FIG. 1.

Other deposition chambers may also benefit from the present disclosureand the parameters listed above may vary according to the particulardeposition chamber used to form the amorphous carbon layer. For example,other deposition chambers may have a larger or smaller volume, requiringgas flow rates that are larger or smaller than those recited fordeposition chambers available from Applied Materials, Inc. In oneimplementation, the boron-carbon film may be deposited using a PRODUCERSE™ or PRODUCER GT™ processing chamber, which is commercially availablefrom Applied Materials, Inc., Santa Clara, Calif. using the parametersset forth in Table I below.

The quantity/percentage of boron in the as-deposited boron-carbon filmmay vary from application to application. The atomic percentage of boronincorporation in the film is calculated as follows: ((B/(B+C) %). Invarious implementations of the present disclosure, the boron-carbon filmmay contain at least 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60,or 65 atomic percentage of boron. The boron-carbon film may contain upto 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 atomicpercentage of boron. The boron-carbon film may contain from about 5 toabout 70 atomic percentage of boron. The boron-carbon film may containfrom about 30 to about 70 atomic percentage of boron. The boron-carbonfilm may contain from about 50 to about 60 atomic percentage of boron.The atomic percentage of carbon incorporation in the film is calculatedas follows: ((C/(B+C) %). The boron-carbon film may contain at least 30,35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 atomic percentage ofcarbon. The boron-carbon film may contain up to 35, 40, 45, 50, 55, 60,65, 70, 75, 80, 85, 90, or 95 atomic percentage of carbon. Theboron-carbon film may contain from about 30 to about 95 atomicpercentage of carbon. The boron-carbon film may contain from about 30 toabout 70 atomic percentage of carbon. The boron-carbon film may containfrom about 35 to about 50 atomic percentage of carbon. The boron-carbonfilm may contain at least 10, 15, or 20 atomic percentage of hydrogen.The boron-carbon film may contain up to 15, 20, or 25 atomic percentageof hydrogen. The boron-carbon film may contain from about 10 to about 25atomic percentage of hydrogen. The boron-carbon film may contain fromabout 15 to about 20 atomic percentage of hydrogen. In certainimplementations where nitrogen is used as a precursor, the boron-carbonfilm may contain at least 2, 5, 8, 10, or 15 atomic percentage ofnitrogen. The boron-carbon film may contain up to 5, 8, 10, 15 or 20atomic percentage of nitrogen. The boron-carbon film may contain fromabout 2 to about 15 atomic percentage of nitrogen. The boron-carbon filmmay contain from about 5 to about 10 atomic percentage of nitrogen.

In general, the following exemplary deposition process parameters may beused to form the boron-containing amorphous carbon layer. The processparameters may range from a wafer temperature of about 400 degreesCelsius to about 700 degrees Celsius (e.g., between about 500 degreesCelsius to about 700 degrees Celsius; between about 550 degrees Celsiusto about 650 degrees Celsius). The chamber pressure may range from achamber pressure of about 1 Torr to about 20 Torr (e.g., between about 2Torr and about 15 Torr; between about 12 Torr and about 15 Torr). Theflow rate of the hydrocarbon-containing gas may be from about 200 sccmto about 5,000 sccm (e.g., between about 200 sccm and about 2,000 sccm;between about 500 sccm and about 700 sccm). The flow rate of a dilutiongas may individually range from about 0 sccm to about 5,000 sccm (fromabout 3,000 sccm to about 5,000 sccm; from about 3,500 sccm to about4,500 sccm). The flow rate of an inert gas may individually range fromabout 0 sccm to about 10,000 sccm (e.g., from about 200 sccm to about2,000 sccm; from about 400 sccm to about 500 sccm). The flow rate of theboron-containing gas mixture may be from about 100 sccm to about 15,000sccm (e.g., between about 200 sccm and about 6,000 sccm; between about4,000 sccm and about 5,000 sccm). The RF power may be between 1,000Watts and 3,000 Watts. The RF power may be between about 1 W/in² andabout 100 W/in² (e.g., between about 3 W/in² and about 20 W/in². Theplate spacing between the top surface 191 of the substrate 190 and thegas distribution assembly 120 may be between about 200 mils to about1000 mils (e.g., between about 200 mils to about 600 mils; between about300 mils to about 400 mils). The boron-carbon film may be deposited to athickness between about 100 Å and about 30,000 Å. The boron-carbon filmmay be deposited to a thickness between about 1,000 Å and about 18,000Å. The boron-carbon film may be deposited to a thickness between about100 Å and about 20,000 Å, such as between about 300 Å to about 5000 Å.The above process parameters provide a typical deposition rate for theboron-containing amorphous carbon layer in the range of about 100 Å/minto about 10,000 Å/min and can be implemented on a 300 mm substrate in adeposition chamber available from Applied Materials, Inc. of SantaClara, Calif.

TABLE I Deposition Exemplary Parameter Exemplary Range Range Temperature(° C.) 400-700° C. 500-700° C. 550-650° C. Pressure (Torr) 1-20.0 Torr2-15 Torr 8-15 Torr RF Power 100-3,000 Watts 1,000-3,000 Watts 2,100Watts (13.56 MHz) Spacing 200-1,000 mils 200-600 mils 320 mils C₃H₆ flow200-5,000 sccm 200-2,000 sccm 500 sccm He flow 0-10,000 sccm 200-2,000sccm 400 sccm H₂ flow 0-5,000 sccm 3,000-5,000 sccm 500-4,500 sccm B₂H₆mixture flow 1,000-15,000 sccm 200-6,000 sccm 4,000 sccm Ar flow0-10,000 sccm 5,000-7,000 sccm 7,000 sccm

The as-deposited boron-carbon film may have a refractive index (n) (633nm)) of greater than 2.5, for example approximately 2.7 (e.g., fromabout 2.5 to about 3.0). The as-deposited boron-carbon film may have a kvalue (k (at 633 nm)) of less than 0.1, for example, (e.g., from about0.01 to about 0.09; from about 0.04 to about 0.06; approximately 0.06 orless). The as-deposited boron-carbon film may have an elastic modulus(GPa) of from about 200 to about 400 MPa (e.g., from about 200 to about350 MPa; from about 210 to about 320 MPa; about 212 GPa). Theas-deposited boron-carbon film may have a stress (MPa) of from about−200 MPa to about 200 MPa (e.g., from about −150 MPa to about 150 MPa;from about −100 MPa to about 100 MPa). The as-deposited boron-carbonfilm may have a density (g/cc) of greater than 1.5 g/cc, for exampleapproximately 1.9 g/cc or higher such as 2.0 g/cc (e.g., from about 1.5g/cc to about 2.5 g/cc; from about 1.5 g/cc to about 2.0 g/cc).

FIG. 2 is a process flow diagram depicting one implementation of amethod 200 for depositing a boron-carbon film according toimplementations described herein. The method 200 begins at operation 210by providing a substrate in a processing volume of a processing chamber.The processing chamber may be the processing chamber 100 depicted inFIG. 1. The substrate may be substrate 190, also depicted in FIG. 1. Thesurface 191 of the substrate 190, as shown in FIG. 3, is substantiallyplanar. Alternatively, the substrate 190 may have patterned structures,for example, a surface having trenches, holes, or vias formed therein.The substrate 190 may also have a substantially planar surface having astructure formed thereon or therein at a desired elevation. While thesubstrate 190 is illustrated as a single body, it is understood that thesubstrate 190 may contain one or more materials used in formingsemiconductor devices such as metal contacts, trench isolations, gates,bitlines, or any other interconnect features. The substrate 190 maycomprise one or more metal layers, one or more dielectric materials,semiconductor material, and combinations thereof utilized to fabricatesemiconductor devices. For example, the substrate 190 may include anoxide material, a nitride material, a polysilicon material, or the like,depending upon application. In one implementation where a memoryapplication is desired, the substrate 190 may include the siliconsubstrate material, an oxide material, and a nitride material, with orwithout polysilicon sandwiched in between.

In another implementation, the substrate 190 may include a plurality ofalternating oxide and nitride materials (i.e., oxide-nitride-oxide(ONO)) (not shown) deposited on the surface 191 of the substrate 190. Invarious implementations, the substrate 190 may include a plurality ofalternating oxide and nitride materials, one or more oxide or nitridematerials, polysilicon or amorphous silicon materials, oxidesalternating with amorphous silicon, oxides alternating with polysilicon,undoped silicon alternating with doped silicon, undoped polysiliconalternating with doped polysilicon, or undoped amorphous siliconalternating with doped amorphous silicon. The substrate 190 may be anysubstrate or material surface upon which film processing is performed.For example, the substrate 190 may be a material such as crystallinesilicon, silicon oxide, silicon oxynitride, silicon nitride, strainedsilicon, silicon germanium, tungsten, titanium nitride, doped or undopedpolysilicon, doped or undoped silicon wafers and patterned ornon-patterned wafers, silicon on insulator (SOI), carbon doped siliconoxides, silicon nitrides, doped silicon, germanium, gallium arsenide,glass, sapphire, low k dielectrics, and combinations thereof.

At operation 220, a hydrocarbon-containing gas mixture is flowed intothe interior processing volume 126. The hydrocarbon-containing gasmixture may be flowed from the gas panel 130 into the interiorprocessing volume 126 through the gas distribution assembly 120. The gasmixture may include at least one hydrocarbon compound. The gas mixturemay further include an inert gas, a dilution gas, a nitrogen-containinggas, or combinations thereof. The hydrocarbon can be any liquid or gas,though the preferred precursor would be vapor at room temperature tosimplify the hardware needed for material metering, control and deliveryto the chamber.

In one implementation, the carbon source is a gaseous hydrocarbon, suchas a linear hydrocarbon. In one implementation, the hydrocarbon compoundhas a general formula C_(x)H_(y), where x has a range of between 1 and20 and y has a range of between 1 and 20. In one implementation, thehydrocarbon compound is an alkane. Suitable hydrocarbon compoundsinclude, for example, alkanes such as methane (CH₄), ethane (C₂H₆),propylene (C₃H₆), propane (C₃H₈), butane (C₄H₁₀) and its isomerisobutane, pentane (C₅H₁₂), hexane (C₆H₁₄) and its isomers isopentaneand neopentane, hexane (C₆H₁₄) and its isomers 2-methylpentane,3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethyl butane, orcombinations thereof. Additional suitable hydrocarbons include, forexample, alkenes such as acetylene, ethylene, propylene, butylene andits isomers, pentene and its isomers, and the like, dienes such asbutadiene, isoprene, pentadiene, hexadiene, or combinations thereof.Additional suitable hydrocarbons include, for example, halogenatedalkenes such as monofluoroethylene, difluoroethylenes,trifluoroethylene, tetrafluoroethylene, monochloroethylene,dichloroethylenes, trichloroethylene, tetrachloroethylene, orcombinations thereof. Additional suitable hydrocarbons include, forexample, alkynes such as acetylene (C₂H₂), propyne (C₃H₄), butylene(C₄H₈), vinylacetylene, or combinations thereof. Additional suitablehydrocarbons include, for example, aromatic hydrocarbons, such asbenzene, styrene, toluene, xylene, ethylbenzene, acetophenone, methylbenzoate, phenyl acetate, phenol, cresol, furan, and the like,alpha-terpinene, cymene, 1,1,3,3,-tetramethylbutylbenzene, t-butylether,t-butylethylene, methyl-methacrylate, and t-butylfurfurylether,compounds having the formula C₃H₂ and C₅H₄, halogenated aromaticcompounds including monofluorobenzene, difluorobenzenes,tetrafluorobenzenes, hexafluorobenzene, or combinations thereof. In oneexample, C₃H₆ is preferable due to formation of more stable intermediatespecies which allows more surface mobility.

Suitable dilution gases such as helium (He), argon (Ar), hydrogen (H₂),nitrogen (N₂), ammonia (NH₃), or combinations thereof, among others, maybe added to the gas mixture, if desired. Ar, He, and N₂ are used tocontrol the density and deposition rate of the amorphous carbon layer.In some cases, the addition of N₂ and/or NH₃ can be used to control thehydrogen ratio of the amorphous carbon layer, as discussed below.Alternatively, dilution gases may not be used during the deposition.

A nitrogen-containing gas may be supplied with thehydrocarbon-containing gas mixture into the processing chamber 100.Suitable nitrogen-containing compounds include, for example, pyridine,aliphatic amine, amines, nitriles, ammonia and similar compounds.

An inert gas, such as argon (Ar) and/or helium (He) may be supplied withthe hydrocarbon-containing gas mixture into the processing chamber 100.Other inert gases, such as nitrogen (N₂) and nitric oxide (NO), may alsobe used to control the density and deposition rate of the amorphouscarbon layer. Additionally, a variety of other processing gases may beadded to the gas mixture to modify properties of the amorphous carbonmaterial. In one implementation, the processing gases may be reactivegases, such as hydrogen (H₂), ammonia (NH₃), a mixture of hydrogen (H₂)and nitrogen (N₂), or combinations thereof. The addition of H₂ and/orNH₃ may be used to control the hydrogen ratio (e.g., carbon to hydrogenratio) of the deposited amorphous carbon layer. The hydrogen ratiopresent in the amorphous carbon film provides control over layerproperties, such as reflectivity.

At operation 230, a boron-containing gas mixture is flowed into theinterior processing volume 126. The boron-containing gas mixture may beflowed from the gas panel 130 into the interior processing volume 126through the gas distribution assembly 120. In one implementation, theboron-containing gas mixture comprises a boron-containing compound andan inert gas. Examples of boron-containing compounds include diborane(B₂H₆), trimethyl boron (TMB or B(CH₃)₃), triethylboron (TEB), methylboron, dimethyl boron, ethyl boron, diethyl boron, ortho-carborane(C₂B₁₀H₁₂) and similar compounds.

In one implementation, the percentage of boron-containing compound inthe total boron-containing gas mixture is from about 2% to about 25%(e.g., from about 10% to about 20%; from about 15% to about 20%; fromabout 2% to about 15%; or from about 4% to about 12%). Exemplaryboron-containing gas mixtures may include 5% B₂H₆/95% N₂, 5% B₂H₆/95%He, 10% B₂H₆/90% He, 5% B₂H₆/95% Ar, 10% B₂H₆/90% Ar, 5% B₂H₆/95% H₂ or20% B₂H₆/80% H₂. It is contemplated that when different concentrationsof boron-containing gas mixtures are used, the flow rate needed toachieve certain film properties may change accordingly. For example inimplementations where 5% diborane is used as the boron-containing gassource, the flow rate of the boron-containing gas mixture may be fromabout 5,000 sccm to about 15,000 sccm, for example, about 13,000 sccm.In another implementation where 10.5% diborane is used as theboron-containing gas source, the flow rate of the boron-containing gasmixture may be from about 4,000 sccm to about 10,000 sccm, for exampleabout 6,000 sccm to about 7,000 sccm. In another implementation where20% diborane is used as the boron-containing gas source, the flow rateof the boron-containing gas mixture may be from about 100 sccm to about6,000 sccm, for example about 4,000 sccm to about 6,000 sccm.

FIG. 2 shows one implementation where the hydrocarbon-containing gasmixture and the boron-containing gas mixture are introduced into theinterior processing volume 126 before turning on the RF plasma inoperation 250. In such an implementation, the hydrocarbon-containing gasmixture may be introduced into the interior processing volume 126 for alonger time such as between about 5 seconds and about 30 seconds, forexample about 15 seconds, which may vary depending upon the size of thesubstrate. The flowing of the hydrocarbon-containing gas mixture priorto the introduction of the boron-containing gas is believed to providecontinuous thermal and pressure stabilization of the interior processingvolume 126. The boron-containing gas mixture is then flowing into theinterior processing volume 126 about 0.5 seconds to about 5 seconds, forexample about 1 seconds to about 2 seconds (the flowing time may vary aslong as the flow is just long enough for the boron-containing gasmixture to start reaching the interior processing volume 126) prior tostriking the RF plasma in operation 250. The process of operation 230may be performed simultaneously, sequentially or may partially overlapwith the processes of operation 220.

Optionally, at operation 240, the pressure in the processing volume isstabilized for a predefined RF-on delay time period. The predefinedRF-on delay time period is a fixed time delay defined as the time periodbetween introduction of the boron-containing gas mixture into theprocessing volume and striking or generating the plasma in operation250. Any suitable fixed time delay may be used to achieve desiredconditions. The length of the RF-on delay time period is typicallyselected such that the boron-containing gas mixture does not begin tothermally decompose or substantially thermally decompose in theprocessing volume. The process of operation 240 may be performedsimultaneously, sequentially or may partially overlap with the processesof operation 220 and operation 230.

At operation 250, after the predefined RF-on delay time period ofoperation 240 expires, RF plasma is generated in the interior processingvolume 126 to deposit a boron-carbon film 304 on the substrate 190. Theplasma may be formed by capacitive or inductive means, and may beenergized by coupling RF power into the precursor gas mixture. The RFpower may be a dual-frequency RF power that has a high frequencycomponent and a low frequency component. The RF power is typicallyapplied at a power level between about 50 W and about 2,500 W, which maybe all high-frequency RF power, for example at a frequency of about13.56 MHz, or may be a mixture of high-frequency power and low frequencypower, for example at a frequency of about 300 kHz. The flow ofhydrocarbon-containing gas mixture and the boron-containing gas mixturemay continue until a desired thickness of the boron-carbon film 304 isreached.

The thickness of the boron-carbon film 304 is variable depending uponthe stage of processing. In one implementation, the boron-carbon filmmay be deposited to a thickness between about 100 Å and about 30,000 Å(e.g., from about 1,000 Å to about 18,000 Å; from about 100 Å to about20,000 Å; from about 300 Å to about 5,000 Å; or from about 1,000 Å toabout 2,000 Å.) Optionally, at operation 260, a plasma purge of theprocessing volume is performed. A purge gas can flow from a purge gassource into the processing chamber 100. The gas distribution assembly120 and support pedestal 150 are energized generating a purge gasplasma. Purge gases which can be used in the processing chamber 100including NH₃, N₂, N₂O, H₃, Ar, He and other suitable plasma purgegases. During the purge process, the heat and pressure can be maintainedin the processing chamber 100. The plasma purge conditions the surfaceof the exposed layer for additional depositions. The conditioned surfaceresults in a smooth interface between layers and better adhesion betweenlayers, as well as better particle control. In some embodiments, arougher interface may be desirable for better layer bonding and adifferent or additional plasma purge process may be performed. After theplasma purge is completed, the energy to the gas distribution assembly120 and the support pedestal 150 can be turned off and a gas purge froma gas purge source flows into the processing chamber 100 to remove allgas contaminants. In one implementation, one or more components of theprecursor gas are stopped during the purge process. For example, if theprocess gas includes a mixture of diborane, propylene and He, the purgegas can only include He and the flow of diborane and propylene isshut-off. In other implementations, a different purge gas or purge gasescan be used.

Additional processing of the substrate 190 may be performed after theprocess of operation 260.

The boron-carbon film 304 may be patterned using a standard photoresistpatterning techniques. A patterned photoresist (not shown) may be formedover the boron-carbon film 304. The boron-carbon film 304 may be etchedin a pattern corresponding with the patterned photoresist layer followedby etching the pattern into the substrate 190. Material may be depositedinto the etched portions of the boron-carbon film 304. The boron-carbonfilm 304 may be removed using a solution comprising hydrogen peroxideand sulfuric acid. One exemplary solution comprising hydrogen peroxideand sulfuric acid is known as Piranha solution or Piranha etch. Theboron-carbon film 304 may also be removed using etch chemistriescontaining oxygen and halogens (e.g. fluorine or chlorine), for example,Cl₂/O₂, CF₄/O₂, Cl₂/O₂/CF₄. The boron-carbon film 304 may be removed bya chemical mechanical polishing (CMP) process.

The flowing the hydrocarbon-containing gas mixture into the processingvolume (operation 220), the flowing a boron-containing gas mixture intothe processing volume (operation 230), optionally stabilizing thepressure in the processing volume (operation 240) and the generating theRF plasma in the processing volume to deposit the boron-carbon film(operation 250) may be repeated until a predetermined thickness isachieved.

EXAMPLES

The following non-limiting examples are provided to further illustrateimplementations described herein. However, the examples are not intendedto be all inclusive and are not intended to limit the scope of theimplementations described herein. Plasma CVD assisted deposition ofvarious Boron, Nitrogen and Carbon containing films were tested andevaluated for their optical properties (n/k/thickness), mechanicalproperties (stress/modulus/hardness/strain-energy), etch selectivity andcompositional/morphological behaviors (B, H, C contents). Based on thesystematic analysis of different film deposition parameters includingtemperature, pressure, boron precursor flow rate, H₂ dilution of theboron precursor, and RF power it was determined that at hightemperatures, the extinction coefficient (k) and stress of boron-carbonfilms was significantly higher than at low temperatures.

Table 1 depicts boron-carbon film properties for an amorphous carbonfilm (APF) reference and a boron-carbon film formed using knowtechniques in comparison with the properties of a high etch selectivityboron-carbon film formed according to implementations described herein.The percentage of boron incorporation in the films is calculated asfollows: ((B/(B+C) %).

TABLE I Proposed High Etch Amorphous Boron- Selectivity Boron- CarbonFilm Carbon Carbon film Item Reference film 550° C. 650° C. Blanket -Oxide Etch     1x 2.5x     3.7x 4.7x Selectivity Blanket - Si/W Etch    1x 0.8x   1x 1.1x Selectivity Density (g/cc)     1.5 1.7    1.9 2.0Stress (MPa)  +50 ~−53  −75 −131 Deposition rate ~4000 4716 4346 4126(A/min) 633 nm n/633 nm k ~2.2/0.4 2.22/0.03 2.5/0.04 2.7/0.06 ElasticModulus (GPa)  ~50 97  212 319 Boron % (XRF) n.a. 61% 60% 59% Hydrogen %(RBS) 12% 36% 22% 15%

FIG. 4A is a plot illustrating the effect of temperature (400° C., 480°C., 550° C., 650° C.) and boron incorporation (12%, 24%, 36%, 48%, 60%)on the deposition rate of boron-carbon films according toimplementations described herein. The y-axis represents the depositionrate (A/minute). The x-axis represents the percentage of boron in thefinal boron-carbon film. As illustrated in FIG. 4A, as the flow rate ofdiborane increases, the deposition rate of the boron-carbon film alsoincreases.

FIG. 4B is a plot illustrating the effect of temperature (400° C., 480°C., 550° C., 650° C.) and boron incorporation (12%, 24%, 36%, 48%, 60%)on the extinction coefficient (k) of boron-carbon films according toimplementations described herein. The y-axis represents the extinctioncoefficient (k). The x-axis represents the percentage of boron in thefinal boron-carbon film. As illustrated in FIG. 4B, as the flow rate ofdiborane increases, the extinction coefficient (k) of the boron-carbonfilm decreases. As further illustrated in FIG. 4B, as the temperatureincreases, the extinction coefficient (k) of the boron-carbon filmincreases.

FIG. 4C is a plot illustrating the effect of temperature (400° C., 480°C., 550° C., 650° C.) and boron incorporation (12%, 24%, 36%, 48%, 60%)on the film density (g/cc) of boron-carbon films according toimplementations described herein. As illustrated in FIG. 4C, as the flowrate of diborane increases, the density of the boron-carbon filmgenerally remains constant. As further illustrated in FIG. 4C, as thetemperature increases, the density of the boron-carbon film increases.

FIG. 4D is a plot illustrating the effect of temperature (400° C., 480°C., 550° C., 650° C.) and boron incorporation (12%, 24%, 36%, 48%, 60%)on the stress (MPa) of boron-carbon films according to implementationsdescribed herein. As illustrated in FIG. 4D, as the flow rate ofdiborane increases, the stress (MPa) of the boron-carbon film decreases.As further illustrated in FIG. 4D, as the temperature increases, thestress of the boron-carbon film increases.

FIG. 5A is a plot illustrating the effect of pressure on the stress andfilm density of boron-carbon films according to implementationsdescribed herein. FIG. 5B is a plot illustrating the effect of spacingon the stress and film density of boron-carbon films according toimplementations described herein. FIG. 5A and FIG. 5B illustrate the useof pressure and spacing to modulate the stress/density of theboron-carbon film. Based on the finding in FIG. 5A and FIG. 5B a stressof less than −100 MPa was targeted at different processing temperatures.

FIG. 6 is a bar graph illustrating the effect of boron percent (60%,52%, and 20%) on oxide etch selectivity and tungsten etch selectivity(oxide or tungsten) at temperatures of 550 degrees Celsius and 650degrees Celsius. As illustrated in FIG. 6, etch selectivity increaseswith temperature but so does stress for similar deposition conditions.As further illustrated in FIG. 6, as boron percent decreases,tungsten-etch selectivity increases but oxide etch selectivity drops.

FIG. 7A is a bar graph illustrating the effect of temperature on theoxide etch selectivity and stress of boron-carbon films according toimplementations described herein. FIG. 7B is a bar graph illustratingthe effect of nitrogen flow rate on the oxide etch selectivity andstress of boron-carbon films according to implementations describedherein. FIG. 7C is a bar graph illustrating the effect of temperature onthe tungsten/silicon etch selectivity and stress of boron-carbon filmsaccording to implementations described herein. FIG. 7D is a bar graphillustrating the effect of nitrogen flow rate on the tungsten/siliconetch selectivity and stress of boron-carbon films according toimplementations described herein. In an approach to modulate stress andimprove W/Si-Etch selectivity, nitrogen-rich Boron-Carbon-Nitride (BCN)hardmask films were evaluated. Nitrogen (N₂) incorporation was achievedby using different flow rates of N₂ gas in tandem with carbon and boronprecursors. A significant increase in deposition rate was achieved byintroducing nitrogen (N₂) into the gaseous deposition mixture. However,nitrogen based byproducts have higher volatility, and henceincorporation of N % is less than 5% in the final boron-carbon film.Therefore, etch selectivity improvements could not be realized. Based onFTIR results we observed that B—C peaks shifts towards C═C or C—N peaks,which should enhance W/Si selectivity. However, lower nitrogenincorporation and higher deposition rates results in breakdown of B—Cmatrix (amorphous morphology), reducing etch selectivity for both oxideand W/Si conditions.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementation of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A semiconductor device, comprising: a boron-carbon amorphous filmdeposited over a substrate, the boron-carbon film comprising from about30 to about 70 atomic percentage of boron, about 30 to about 70 atomicpercentage of carbon, and about 10 to about 25 atomic percentage ofhydrogen.
 2. The semiconductor device of claim 1, wherein theboron-carbon amorphous film has an elastic modulus (GPa) from about 200to about 400 MPa.
 3. The semiconductor device of claim 1, wherein theboron-carbon amorphous film has less than 5 atomic percentage ofnitrogen.
 4. The semiconductor device of claim 1, wherein theboron-carbon amorphous film has a stress (MPa) less than 0 MPa.
 5. Thesemiconductor device of claim 4, wherein the boron-carbon amorphous filmhas the stress (MPa) of about −75 MPa.
 6. The semiconductor device ofclaim 4, wherein the boron-carbon amorphous film has the stress (MPa) ofabout −131 MPa.
 7. A method of processing a substrate in a processingchamber, comprising: exposing the substrate to a boron-containing gasmixture and a hydrocarbon-containing gas mixture in the presence of RFpower to deposit a boron-carbon amorphous film over the substrate,wherein the substrate is heated to a substrate temperature from about400 degrees Celsius to about 700 degrees Celsius, and the boron-carbonfilm comprises from about 30 to about 70 atomic percentage of boron,about 30 to about 70 atomic percentage of carbon, and about 10 to about25 atomic percentage of hydrogen.
 8. The method of claim 7, wherein theboron-carbon amorphous film has an elastic modulus (GPa) from about 200to about 400 MPa.
 9. The method of claim 7, wherein the boron-carbonfilm has a stress from about −100 MPa to about 100 MPa.
 10. The methodof claim 7, wherein the boron-carbon amorphous film is deposited byexposing the substrate to a boron-containing gas mixture comprisingdiborane (B2H6) and a hydrocarbon-containing gas mixture comprisingpropylene (C3H6).
 11. The method of claim 7, further comprising:exposing the substrate to a nitrogen-containing gas, and theboron-carbon amorphous film has less than 5 atomic percentage ofnitrogen.
 12. The method of claim 7, further comprising: prior to theexposing the substrate to a boron-containing gas mixture and ahydrocarbon-containing gas mixture in the presence of RF power,stabilizing a pressure in the processing chamber for a predefined RF-ondelay time period.
 13. The method of claim 12, wherein the predefinedRF-on delay time period is between about 0.1 seconds and 5 seconds. 14.A method of processing a substrate in a processing chamber, comprising:exposing the substrate to a boron-containing gas mixture comprisingdiborane (B2H6) and hydrogen-containing gas in the presence of a mixtureof high-frequency RF power delivered at 13.56 MHz and low-frequency RFpower delivered at 300 kHz to deposit a boron-carbon amorphous film overthe substrate, wherein the boron-carbon amorphous film comprises fromabout 30 to about 70 atomic percentage of boron, about 30 to about 70atomic percentage of carbon, and about 10 to about 25 atomic percentageof hydrogen.
 15. The method of claim 14, wherein the boron-carbonamorphous film has an elastic modulus (GPa) from about 200 to about 400MPa and a stress from about −100 MPa to about 100 MPa.
 16. The method ofclaim 14, further comprising: prior to the exposing the substrate to thegas mixture, stabilizing a pressure in the processing chamber for apredefined RF-on delay time period.
 17. The method of claim 16, whereinthe predefined RF-on delay time period is between about 0.1 seconds and5 seconds.
 18. The method of claim 14, wherein the gas mixture contains5% or 20% of diborane and 80% or 95% of hydrogen-containing gas.
 19. Themethod of claim 16, wherein the predefined RF-on delay time period is afixed time delay defined as a time period between flowing theboron-containing gas mixture into the processing chamber and generatingan RF plasma.
 20. The method of claim 19, wherein a length of thepredefined RF-on delay time period is selected so that theboron-containing gas mixture does not begin to thermally decompose orsubstantially thermally decompose in a processing volume of theprocessing chamber.